'High-normal' blood pressure in young adults spells risk of heart failure in later life

http://www.eurekalert.org/pub_releases/2015-06/jhm-bp062215.php

Public Release: 22-Jun-2015
Johns Hopkins Medicine

Mild elevations in blood pressure considered to be in the upper range of normal during young adulthood can lead to subclinical heart damage by middle age -- a condition that sets the stage for full-blown heart failure, according to findings of a federally funded study led by scientists at Johns Hopkins.

A report on the findings of the multicenter study that followed 2,500 men and women over a period of 25 years is published online June 22 in the Journal of the American College of Cardiology.

Persistently elevated blood pressure, or hypertension, is one that tops 140/90, a reading that measures the force of pressure in the heart as it contracts (top number) and as it relaxes between contractions (bottom number). Hypertension has been long implicated as a risk factor in a range of cardiovascular diseases. But the new study suggest that pressure just below that threshold -- or high normal pressure -- begins to fuel heart damage in people as young as 20 and can lead to changes in heart muscle function in as little as 25 years.

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The latest clinical guidelines issued by the Joint National Committee in 2014 define hypertension as blood pressure above 140/90, but they call on clinicians and patients to aim for a pressure below 150/90. However, results of the new study suggest that a single cutoff measurement does not apply to all ages, and what constitutes 'normal' should probably change with age.

In healthy people, blood pressure tends to rise slightly as they grow old, researchers say, so while 150/90 may be a reasonable target for a 60-year-old, it may be too high for a 28-year-old.

'A number of patients in our study had 'high-normal' blood pressure in their 20s and 30s but by the time they were 45, they had the heart function of a 75-year-old even if they never met the clinical definition of hypertension,' Lima says.

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Compared with people with the lowest diastolic pressure -- the bottom number in a reading -- those with highest diastolic pressure were 70 percent more likely to show signs of abnormal relaxation, a harbinger of a particularly pernicious, treatment-resistant form of heart failure in which the muscle contracts normally but is incapable of relaxing.

Those with persistent elevations in their top readings, or systolic blood pressure, were 46 percent more likely have abnormal contraction, which typically leads to a form of heart failure marked by the organ's inability to contract and pump out blood. Systolic pressure signals the pressure in the arteries during contraction as the heart pumps out blood. The bottom number, or diastolic pressure, indicates the pressure during relaxation, or between contractions.

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